The manufacture of terpene-phenol resins with low softening points (that is, softening points in the range of from about 80.degree. C. to about 110.degree. C.) is very difficult. The traditional methods for producing such resins use one of two approaches. In the first approach diluents such as mineral oil or polyolefin oligmers are added to resins having higher softening points. This approach usually results in reduced adhesive or ink formulation performance or excessively high amounts of volatiles in the resulting resin. In addition, the use of diluents and consequent extra handling of the resin increases the cost of the final product.
The second approach is to synthesize the low softening point resin directly. Generally, the synthetic methods in current use produce base resins that cannot be finished to softening points below 110.degree. C. without leaving substantial amounts of process solvents and/or phenol in the resin. Again, this results in decreased adhesive or ink formulation performance.
For example, U.S. Pat. No. 3,929,938 discloses processes for producing limonene-phenol condensation products using relatively low reaction temperatures (from about 10.degree. C. to about 45.degree. C.). However, the products have high softening points (greater than 140.degree. C.). Thus, the process does not produce the desired low softening point products.
The process disclosed in U.S. Pat. No. 3,993,626 also produces phenol-modified hydrocarbon resins for use in printing inks. However, the process produces products with softening points well above the desired range (greater than 120.degree. C.).
One route which might circumvent the problem of leaving substantial amounts of process solvents in the resin is taught in U.S. Pat. No. 4,056,513, which discloses that .DELTA..sup.3 -carene and another terpene, such as .alpha.-pinene, may be reacted with phenol using a three-step polymerization sequence using different temperatures in each step. The practice of the process requires the initial addition of about one-half of the desired .DELTA..sup.3 -carene to a mixture of phenol and boron trifluoride. The boron trifluoride is used as the gas or as one of its usual complexes. A diphenolcarene is produced by the initial reaction at temperatures of between 80.degree. C. and 120.degree. C. The remainder of the .DELTA..sup.3 -carene, with additional boron trifluoride compound, is then added to the diphenolcarene resin and reacted at a temperature between 80.degree. C. and 120.degree. C. for further condensation. Finally, upon completion of the .DELTA..sup.3 -carene-phenol condensation, an active terpene is added to the reaction mixture and cooked at temperatures over 100.degree. C.
The process is time consuming and is not convenient on a large scale. The use of other terpenes, such as .alpha.-pinene, .beta.-pinene, dipentene and/or limonene, alone results in resins with higher softening points and wider ranges of softening points. Since .DELTA..sup.3 -carene is not readily available except in a few regions of the world, the process is of little use commercially in the United States.
Of much more use to U.S. industries would be a process for producing a low softening point terpene-phenol resin using a more readily available terpene, such as .alpha.-pinene, .beta.-pinene, dipentene and/or limonene. These terpenes are readily available from coniferous and citrus plants grown throughout the world. In addition, for commercial reasons it is desirable to provide a method for producing the resin using as few steps, and as few temperature changes, as possible.
The process of U.S. Pat. No. 4,701,517 provides a means for producing a terpene-phenol copolymer with lowered ring and ball softening points. The process uses boron trifluoride complexes to form the copolymers. However, the lowering of the softening point is afforded only by the addition of vinyl aromatics, such as styrene, in the copolymerization process. The resulting vinyl aromatic-terpene-phenol terpolymer has a lowered softening point but at the expense of the necessary addition of the vinyl aromatic which increases the expense of the reaction. In addition, the presence of vinyl aromatics are known to decrease the compatibility of the resulting resin with the materials used for adhesives and ink formulations.
The process of U.S. Pat. No. 3,625,874 provides a phenol-cyclic polyolefin reaction product but also requires a two-step reaction process. The boron trifluoride complex used in the process is eliminated between the first and the second step.
The process of U.S. Pat. No. 3,976,606 also discloses a method for making terpene-phenolic resins which uses a boron trifluoride complex. Again, however, the process uses a two-step reaction which increases the cost of the final product as well as the time required to produce the material.
The prior art and current practice for the production of low softening point terpene-phenol resins are expensive and time consuming. The current reaction schemes require exotic materials, such as carene, or several steps and/or a variety of temperatures to produce a useable resin.
It is an object of the present invention to provide a method for producing a terpene-phenol resin having a ring and ball softening point in the range of from about 80.degree. C. to about 110.degree. C.
In addition, it is an object of the present invention to provide such a method for producing a terpene-phenol resin wherein the terpene is .alpha.-pinene, .beta.-pinene, dipentene, limonene and/or .DELTA..sup.3 -carene.
Further, it is an object of the present invention to provide a method for preparing a terpene-phenol resin having a ring and ball softening point in the desired range in a single-step-single-temperature process.